Written when Maine de Biran was coming into his philosophical maturity, in 1807, 'Of Immediate Apperception' was the first complete statement of his own philosophy of the will. It was the winning entry to a competition organised by the Berlin Academie des Sciences et Belles-Lettres on the subject of self-awareness and of the possibility of an 'immediate apperception' of the self. It contains the core of Biran's philosophy of effort, as it is developed in dialogue with the tradition of British empiricism in particular. Notably, it is in this work that Biran first reflects on the 'lived body' and it marks the moment in which he fully accomplishes his break away from Condillac and the Ideological school. With enlightening critical apparatus, including an editor's introduction, glossary, and bibliography, the publication of this edition shows how Biran's work is pivotal for the development of French philosophy, and makes clear his influence on the later writings of Ravaisson and Bergson.